1. Field of the Invention
The present invention relates to driving an input signal, and more particularly, to a driver for driving a light emitting device such as an organic light emitting diode (OLED).
2. Description of the Prior Art
A very large voltage (e.g. a driving voltage of 13V) is required to drive a conventional organic light emitting diode (OLED). As a result, a corresponding driving stage should be designed to work at 13V as well. To fabricate transistors capable of enduring such a high voltage swing, a high voltage (HV) semiconductor process is required. These HV devices are usually very large in size and consume a huge amount of power; in addition, if the OLED driver is designed to be integrated with a static random access memory (SDRAM), the HV device semiconductor process is the only choice and therefore the integration is implemented at the expense of the chip area and power consumption.
Please refer to FIG. 1, which is a diagram of a conventional OLED driver 100 and an OLED 101. The OLED driver 100 includes a driving stage 110 and an output stage 120. The driving stage 110 includes a level shifter 111, a digital-to-analog converter (DAC) 112, and a buffer 113. The output stage 120 includes a switch transistor M1 for receiving a switch signal SEL, a storage capacitor C and an output transistor M2. Since an output signal VOUT from the OLED driving stage 110 has a voltage swing of 13V to drive the output stage 120 to generate an output current IOUT, digital input signals VIN[5:0] are converted into a plurality of digital signals with a voltage swing of 13V by the level shifter 110, and then the converted digital signals are further converted into an analog signal by the DAC 120. Finally, the buffer 113 receives the analog signal to output the output signal VOUT.
As can be seen in FIG. 1, all the components within the driving stage 110 are forced to work under a supply voltage of 13V, leading to a very large amount of power consumption and chip size.